Patent GB-1131918-A (GB)
Title: Jet injector
IPC: A61M5/34
Filed: 1966-04-27
Abstract: 1131918 Needleless hypodermic syringe M B BURGESS 27 April 1966 [6 May 1965] 18370/66 Headings F1A A1A3 A1A7 A1C1 A3A1A A4L A4Q and A4S4 In a needleless jet injector wherein a cylinder member and a piston member are arranged for co-operative engagement to define a chamber of variable volume and wherein each of the cylinder and piston members includes a one-way valve communicating with the chamber, one member includes a cannula arranged for connection to a reservoir of medicinal liquid, the valve of the member including the cannula being in communication with the cannula and being arranged to provide flow from the reservoir into the chamber, and the other member includes a jet discharge orifice, the valve of the member including the orifice being arranged to provide flow from the chamber through the orifice. The injector further comprises an actuating device operable to impart a powerful compression movement to one member with respect to the other member in order rapidly to reduce the volume of the chamber thereby to  cause ejection of liquid through the orifice. As illustrated in Figs. 1 and 2, views of the injector before and after cocking, respectively, a chamber 18 of variable volume is defined by reciprocable piston member 16 and housing member 10. The housing member includes a cylinder 32 to which a nose piece 34 is attached by a threaded collar 36, a nozzle tip 38 being threadedly attached to the nose piece to position an orifice plate 40, in the centre of which is a jet orifice 12. At least one strainer screen 42 is held within the nose piece by a conical spring 44, which serves also as the operating spring for a one-way valve 14 consisting of a spherical member made of rubber, nylon or polytetrafluoroethylene and arranged to provide flow from the chamber to the orifice. Threadably attached to the cylinder of the housing member is a tube 50, which is threadably attached to a top tube 52, which in turn is threadably attached to a clevis block 54, which includes pivot pins 56 and 58 for pivotally supporting a lever 26 and a latch 30, respectively. The reciprocable piston member includes piston 20 and a one-way valve 22, which comprises a floating check-plate 60 provided with at least one off-centre axial bore and arranged to provide flow from a reservoir 24 through a passage 100 formed centrally of the piston to the chamber. Threadably secured to the piston are a cannula 62 and a cartridge tube 64, which includes a flange 65 engaged by actuating spring 28. Sealing between the cylinder and the piston is improved by a rubber O-ring 46, which is positioned by a retainer ring 48 threadably secured to the cylinder. The cartridge tube encloses a reservoir of for example medicinal fluid, for example a standard ampoule cartridge comprising a glass tube 68 having a slidable rubber stopper 70, which is movable by light biasing spring 76 and associated tip member 78 to compensate for withdrawal of liquid from the cartridge, and a piercable seal for example in the form of a rubber membrane closure 72 which is piercable by tip 74 of the cannula. Mounted on the lever pivot pin is a latch spring 80 having double arms 82, which straddle and bias the rotatable latch in a clockwise direction (as illus-  trated) and arms 84 which straddle and bias the rotatable lever also in a clockwise direction (as illustrated). Before cocking, see Fig. 1, the engagement fingers 86 of the latch rest on a flanged portion 88 of a spring cap 66, which is threadably secured to the cartridge tube, and a finger portion 92 of the lever engages below the flanged portion of the spring cap; after cocking, see Fig. 2, the finger portion is situated between the engagement fingers which now also engage below the flanged portion of the spring cap; after cocking, see Fig. 2, the finger portion is situated between the engagement fingers which now also engage below the flanged portion of the spring cap; on further depression, the lever pivots about a shoulder 94 of the clevis block, slotted lever pivot pin opening 90 allowing the finger portion and the engagement fingers to disengage the flanged portion of the spring cap thereby to allow the actuating spring to effect rapid movement of the piston member relative to the housing member whereby the volume of the chamber is reduced. Window openings 102 and 104 are provided in the tube of the housing and in the cartridge tube, respectively, to enable the level of liquid in the cartridge to be determined and to facilitate exchange of cartridges. Instead of using an ampoule cartridge, the tip of the cannula may be connected to flexible tubing leading via aperture 110 in the spring cap to an external liquid reservoir source, for example a collapsible plastics bottle; use of an external liquid source makes the light biasing spring and associated tip member unnecessary.